Rotary fluid equipment, such as centrifugal pumps, usually includes a rotary operative member such as an impeller which is driven by a prime mover such as an electrical motor. A rotary shaft connects the prime mover to the operative member. Typically the operative member is contained within its own housing, having an inlet and an outlet for the fluid being moved, and the shaft is also contained within a shaft housing. The shaft may be supported by bearings and usually there will be seals engaging the shaft to prevent fluid which enters the shaft housing from reaching the prime mover. The seals, shaft and shaft housing define a seal cavity which opens towards the housing containing the operative member.
During operation of the rotary fluid equipment particulate contaminant material carried into the equipment by the moving fluid, or eroded from the adjacent surfaces with the housing, can enter the seal cavity and damage the shaft and/or the seals unless some type of protector is arranged at the entrance to the seal cavity.
There have of course been attempts in the past to protect the seal cavity. Most such attempts have involved the attachment of a plate or other member to the rotor at the entrance to the seal cavity to aid in eliminating air (U.S. Pat. No. 3,070,028) or to prevent fluid from entering the seal cavity when the equipment comes to a halt (U.K. Pat. No. 212,879). Other attempts involve labyrinth type seals which involved elements on the shaft and the shaft housing which are interdigitated to increase the difficulty for contaminants to enter the seal cavity (U.S. Pat. Nos. 2,834,618; 2,874,982; 4,185,838 and 4,335,886). None of these prior art arrangements have simply or inexpensively been an appropriate solution to the problem.